The work aims to establish accurate top-down estimates of the surface sources and sinks for important greenhouse gases, including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and carbon monoxide (CO) over North America, and address individual science questions, particularly with regard to the causes of variability on diurnal, seasonal, and interannual timescales that underlie these estimates. Collocated airborne and tower-based measurements of these gases for selected months in the period 2003-2011 will be analyzed using a receptor-oriented Lagrangian particle dispersion model driven by a version of the Weather Research and Forecasting (WRF) model adapted to flux inversion work. The analysis will provide an assessment tool for independent bottom-up emission estimates from existing inventories. The availability of reliable transport fields and a conjoint analysis of the four gases will be critical to the success of the study.
Human-induced changes in atmospheric concentrations of greenhouse gases are a major societal concern discussed in the press, in Congress, and by ordinary citizens every day. Currently there is no validation for inventory-based estimates of U.S. and North American contributions to this global problem, and there are indications that these estimates may be in error.
The work will decisively improve this situation by providing new assessments based on strong physical and observational constraints. The data, results, and software will be made publicly available during the research, and the principal investigators will engage in public outreach by communicating the results that are pertinent to the public debate on climate change.
During the reporting period, scientists at CU CIRES contributed to the testing of the WRF-STILT Lagrangian Particle Dispersion Model (LPDM) framework. Together with the project team at AER, lead by Janusz Eluszkiewicz, we implemented several simulations using different set of parameterization to investigate the sensitivity of the calculated emission influence functions (footprints) to different model set-ups. We also participated in the intercomparison of various LPDMs. We conducted large set of simulations for multiple years to provide a library of results that could be further used in emissions optimization projects by several graduate students in US Universities. CIRES scientists involved in this project are co-authors on several of the peer-reviewed papers that used the products of this NSF funded project. Adam Hirsch was the original CIRES PI on the project. Gourdji, S. M., K. L. Mueller, V. Yadav, D. N. Huntzinger, A. E. Andrews, M. Trudeau, G. Petron, T. Nehrkorn, J. Eluszkiewicz, J. Henderson, D. Wen, J. Lin, M. Fischer, C. Sweeney, and A. M. Michalak (2012), North American CO2 exchange: intercomparison of modeled estimates with results from a finescale atmospheric inversion, Biogeosciences, 9, 457–475. Kort E. A., A. E. Andrews, E. Dlugokencky, C. Sweeney, A. Hirsch, J. Eluszkiewicz, T. Nehrkorn, A. Michalak, B. Stephens, C. Gerbig, J. B. Miller, J. Kaplan, S. Houweling, B. C. Daube, P. Tans, and S. C. Wofsy (2010), Atmospheric constraints on 2004 emissions of methane and nitrous oxide in North America from atmospheric measurements and receptor-oriented modeling framework, J. Integr. Environ. Sci., 7:2, 125-133. Miller, S. M. E. A. Kort, A. I. Hirsch, E. J. Dlugokencky, A. E. Andrews, X. Xu, H. Tian, T. Nehrkorn, J. Eluszkiewicz, A. M. Michalak, and S. C. Wofsy (2012) Regional sources of nitrous oxide over the United States: Seasonal variation and spatial distribution, J. Geophys. Res. 117 , D06310, doi:10.1029/2011JD016951. Zhao, C., A. E. Andrews, L. Bianco, J. Eluszkiewicz, A. Hirsch, C. MacDonald, T. Nehrkorn, and M. L. Fischer (2009), Atmospheric inverse estimates of methane emissions from Central California, J. Geophys. Res., 114, D16302, doi:10.1029/2008JD011671.
